Is PMRT routinely recommended for all patients with positive lymph nodes after neoadjuvant chemotherapy?

This is a good question. In general at MD Anderson, we tend to recommend post-mastectomy radiation therapy for patients with residual micro- or macro-metastatic disease in the axillary nodes after neoadjuvant chemotherapy. This recommendation is strong when the patient had clinical stage III disease at presentation or had clinical stage II disease at presentation but there were multiple (>= 3) involved microscopic nodes pathologically after chemotherapy or if the tumor were particularly large (> 5 cm) after chemotherapy. In addition, if an axillary lymph node dissection were omitted, this would also strengthen the recommendation for PMRT.

There is a sizeable group of patients with clinical stage II disease at presentation who, after neoadju...

The prognosis and outcome for micrometastases after neoadjuvant chemotherapy is not the same as the same volume of disease before chemotherapy. The NSABP study showed that micrometastases in nodes after chemo is predictor for worse outcome in comparison to node negative disease and thus should be interpreted differently.

I agree with @Dr. First Last that the "biology" of the tumor should be a consideration in this setting, and this also applies in the context of ER+ disease. In addition to TNBC and HER2 amplified disease, patients with luminal B type tumors (ER+, HER2-, grade 3 and/or high Ki67, high oncotype, or by molecular classification such as PAM50) have very poor outcomes with residual axillary disease after neoadjuvant chemotherapy and therefore are not good candidates for treatment de-intensification in the absence of new prospective data. However, luminal A tumors (ER+, Her2-, grade 1-2, low Ki67, low oncotype etc) and invasive lobular carcinomas for that matter are unlikely to be chemosensitive and therefore low volume residual axillary disease a...